I have the Microair 760 and the M-2000 transponder with mode S .  The good and the bad follows .
1.  In 7 years only had one problem with the Microair 760 (VHF) and that was an internal ground that was bad .  There is a Microair repair facility on the East coast that fixed the problem and updated the latest mods .
2.  SOCAL radar did not like the Microair transponder .  As it turned out a Mod 7 update fixed that...however the last time I checked there were no radio shops in the US that would attempt repair on a Microair transponder .  Had to send it back to AUS to the factory to get the update .  While it was there they gave it good going thru .  Other than that "bug" in the unit it has worked 4.0 for 7 years .  There may be a transponder repair facility at the time of this printing , I just don't know .
PROS...
1. VERY light weight.
2. Small size.
3. Fits in the panel.
4. Easy to operate .
CONS...
1. Repairing can sometimes be a challenge .
Have not had any static or engine related noises making there way into the radio or transponder .  Sounds like some sort of "filter" may fix that problem ?   

   This may require the expertise of Mr. Electron !   
 
 RB   
